1. The Field of the Invention
The present invention relates to orthodontic brackets, and more particularly to orthodontic brackets made from specific polymeric compositions that comprise at least one type of crystalline polymer.
2. The Relevant Technology
Orthodontics is a specialized field of dentistry that involves the application of mechanical forces to urge poorly positioned, or crooked, teeth into correct alignment and orientation. Orthodontic procedures can be used for cosmetic enhancement of teeth, as well as medically necessary movement of teeth to correct underbites or overbites. For example, orthodontic treatment can improve the patient's occlusion, or enhanced spatial matching of corresponding teeth.
The most common form of orthodontic treatment involves the use of orthodontic brackets and wires, which together are commonly referred to as “braces”. Orthodontic brackets, more particularly the orthodontic bases, are small slotted bodies configured for direct attachment to the patient's teeth or, alternatively, for attachment to bands which are, in turn, cemented or otherwise secured around the teeth. Once the brackets are affixed to the patient's teeth, such as by means of glue or cement, a curved arch wire is inserted into the slot of each bracket. The arch wire acts as a template or track to guide movement of the teeth into proper alignment. End sections of the arch wire are typically captured within tiny appliances known as “buccal tubes” affixed to the patient's molars.
Customarily, an arch wire is held within the arch wire slot by ligatures. More recently, self-ligating brackets have been developed that eliminate the need for separate ligatures. Self-ligating brackets may include a cover associated with the bracket base that closes over and secures the arch wire within the arch wire slot. Examples of self-ligating brackets are disclosed in U.S. Pat. Nos. 3,748,740, 4,077,126, 5,857,849, and 6,071,118.
Conventional brackets requiring ligatures and self-ligating brackets have been formed from a wide variety of materials, including metal, plastic, or a combination thereof. Often brackets made from plastic are fragile and easily damaged, partly because of bracket design, but also because of choice of materials. Because of these difficulties, there is a continuing need for more robust designs, but particularly there is a need for materials from which a bracket may be manufactured to increase strength and durability, while maintaining sufficient flexibility where flexibility is needed.